Zhou Y Y, Lakatta E G, Xiao R P
Laboratory of Cardiovascular Science, Gerontology Research Center, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, USA.
Drugs Aging. 1998 Aug;13(2):159-71. doi: 10.2165/00002512-199813020-00007.
The calcium current is one of the most important components in cardiac excitation-contraction coupling. During aging, the magnitude of L-type Ca++ channel current (ICa,L) is significantly increased in parallel with the enlargement of cardiac myocytes, resulting in unaltered ICa,L density. Since the inactivation of ICa,L is slowed and the action potential duration is prolonged, the net Ca++ influx during each action potential is likely to be increased in senescent hearts relative to young ones. This augmentation of Ca++ influx may be important for the preserved cardiac function of the older heart in the basal state. However, it increases the risk of Ca++ overload and Ca(++)-dependent arrhythmias in the senescent heart. During stress, the response of ICa,L to beta-adrenergic receptor stimulation is markedly reduced, which may be an important cause of the age-related decrease in cardiac reserve function. These age-dependent changes in ICa,L and its modulations are similar to those observed in the enlarged myocytes of the hypertrophied and failing heart.
钙电流是心脏兴奋 - 收缩偶联中最重要的组成部分之一。在衰老过程中，L型Ca++通道电流（ICa,L）的幅度随着心肌细胞的增大而显著增加，导致ICa,L密度不变。由于ICa,L的失活减慢且动作电位持续时间延长，与年轻心脏相比，衰老心脏每次动作电位期间的净Ca++内流可能会增加。这种Ca++内流的增加对于老年心脏在基础状态下维持心脏功能可能很重要。然而，它增加了衰老心脏中Ca++过载和Ca(++)依赖性心律失常的风险。在应激期间，ICa,L对β-肾上腺素能受体刺激的反应明显降低，这可能是与年龄相关的心脏储备功能下降的重要原因。ICa,L及其调节的这些年龄依赖性变化与在肥厚和衰竭心脏的增大心肌细胞中观察到的变化相似。
